Reliability, cost efficiency, and ease of use make magnetic media, such as magnetic tape, the medium of choice for many information storage and retrieval applications. Magnetic media may be made more useful and cost effective by increasing the areal density of stored information. One way of increasing areal density is to increase the track density. Track density determines the number of data tracks capable of being written onto a given width of magnetic media. Increasing the track density requires either an increase in the accuracy of head positioning or a head capable of reading and writing more closely spaced multiple tracks.
A recording head generally contains multiple write elements to simultaneously write multiple tracks for achieving a high rate of data transfer. Each write element typically includes a yoke constructed of a magnetic material. Current flowing through a conductive coil encircling a portion of the yoke induces magnetic flux in the yoke. A magnetic field is created across a gap in the yoke, inducing magnetic field patterns on magnetic media traveling by the recording head.
Constructing a recording head using thin film techniques permits the small element geometry required for high areal density recording and reduces costs by applying replication and manufacturing techniques similar to those used in integrated circuit production. Thin film write elements are typically built on a substrate with the conducting coil constructed as a spiral parallel to the substrate. The conductive coil therefore requires substantial substrate area, limiting how closely adjacent write elements can be spaced.
In tape systems, interleaving may be used to compensate for the problem of large spacing between write element gaps. In an interleaved tape system, adjacent data tracks are not written in the same pass requiring multiple passes of the tape head over the magnetic tape to fill all the data tracks. Interleaving requires highly accurate head-to-track positioning systems to properly align write gaps with data tracks. As track density increases, the head positioning accuracy to support interleaving becomes increasingly difficult.
Several designs have been proposed to reduce the spacing between write elements. In one design, the conductive coil is wound about the yoke with each loop substantially normal to the substrate. The yoke is constructed such that flux circulates in a path parallel to the substrate, limiting how closely adjacent yokes can be spaced. In addition, the recording gap is normal to the substrate, requiring difficult and complex manufacturing processes to achieve desired gap dimensions and limiting the placement of write elements in a multiple element head structure.
In another design, an array of write elements is formed with current supplied to a particular element from a row signal and a column signal in much the same way that a memory element is accessed. While this design permits close element spacing, its requirement for precise timing of row and column current pulse signals necessitates a complicated control system that limits the data rate.
The ability to read data from a particular data track while rejecting the effects of closely spaced adjacent tracks can be enhanced by using alternating write element gap azimuth angles. The gap azimuth angle can be defined as the angle made by the gap opening relative to a reference line drawn through the center of the gaps. Typical azimuth angles may alternate between +15° and −15° or more for adjacent write gaps.
What is needed is a write element design permitting close spacing of recording gaps, alternating azimuth angles between gaps, and the ability to place elements in a variety of two dimensional geometric configurations. Each write element should have a gap opening that can be constructed using standard thin film processing techniques. The write elements should be electrically driven by conventional, non-array means.